The success of the 3G and 4G cellular communication technologies, together with the success of Wi-Fi, has spurred explosive growth of wireless traffic. It is expected that broadband access via smartphones and other devices is going to be ubiquitous, and billions of devices will be connected—mostly wirelessly—to become part of the so-called Internet of Things (IoT). This trend presents tremendous opportunities—and challenges—for wireless communication to provide connectivity and capacity for these billions of people and machines.
In a wireless communication device, a transceiver is a unit that performs the function of both a transmitter and a receiver. Typically, a transceiver interfaces with a lower-frequency unit (e.g., an intermediate frequency (IF) unit) and digital processors (e.g., a baseband unit) at one end, and antennas at the other. In transmit (TX) mode, the transceiver receives the outgoing signals from the digital processors and/or lower-frequency units and performs functions such as I/Q modulation, frequency conversion (i.e., up-conversion to radio frequency (RF) signals), filtering, phase shifting, amplification, and the like. The amplified signals are then radiated over the air via the antennas. In receive (RX) mode, the transceiver receives the incoming RF signals from the antennas and performs functions such as amplification, filtering, phase shifting, frequency conversion (i.e., down-conversion to IF or baseband signals), FQ demodulation, and the like. The output of the receiver is then fed into the lower-frequency units or digital processors for further processing, such as channel estimation, MIMO processing, demodulation, decoding, and additional processing further up in the communication and networking protocol stack. In a device that supports beamforming or multiple-input-multiple-output (MIMO) operations, there are often multiple transceivers in an RF unit.
A typical wireless communication device may comprise a radio frequency (RF) unit, an intermediate frequency (IF) unit, a baseband (BB) unit, and a network processor. The RF unit may include at least one transceiver that operates in at least one frequency band within the frequency range from a few hundred megahertz to a few hundred gigahertz. The RF unit communicates with the intermediate frequency (IF) unit and baseband unit via a data interface and a control interface. Typically, the baseband unit or the network processor controls the configurations and operations of the transceivers. That is, the baseband unit or network processor sends control commands to the RF unit to switch the transceiver between TX mode and RX mode, and change other configurations of the RF unit. The control command is typically sent to the RF unit via a control interface that is separate from the data interface, which may comprise multiple data communication ports. Note the control interface may share the same physical connection or wires with the data interface.
However, in certain situations, a user may find it advantageous to use the RF unit in conjunction with another device. For example, the RF unit may operate in a millimeter-wave frequency band, such as the 24 GHz, 28 GHz, 37 GHz, or 39 GHz bands. Another device may perform networking, baseband processing, and also transceiver operations with a lower operating frequency at 2.4 GHz or 5 GHz (e.g., a Wi-Fi or Wi-Fi-based device). For simplicity, this separate device may be generically referred to as the “IF and baseband unit”. The RF unit can then interface with this IF and baseband unit, performing the frequency conversion between 2.4 GHz (or 5 GHz) and the millimeter-wave frequency bands.
However, many times these Wi-Fi or Wi-Fi-based devices lack the control interface to control an external RF unit. In particular, since Wi-Fi devices transmit and receive in the same frequency, these devices either work in transmit mode or receive mode at any time instance. The transmission/reception (TX/RX) mode switch signal may not be readily available for the RF unit that is external to the Wi-Fi or Wi-Fi based devices. This lack of a TX/RX mode control signal prevents the easy integration of an RF unit with an off-the-shelf IF and baseband unit.
Therefore, there is a need in the art for an improved modular wireless communication device. In particular, there is a need for a modular RF unit that may be easily integrated with a modular IF and baseband unit without the need for a TX/RX control signal from the IF and baseband unit that controls the transmit/receive mode of the RF unit.